The fuel-air or other fuel-oxidizer combustion that occurs within internal combustion engines produces a significant amount of heat that is typically dissipated by the walls of the cylinders and through the piston. It is estimated that as much as 50 percent of the available mechanical power that could be generated from an internal combustion engine is lost as heat. Engine cooling creates the mechanism for extracting heat out of the combustion gases, which reduces the amount of mechanical power that can be extracted from these gases. As a result, this dissipation of heat greatly reduces the efficiency of the engine. For example, in a car, it is estimated that about 25% of the available chemical energy from the fuel-oxidizer combustion in the engine is dissipated through the radiator. This is comparable to the fraction of total available power that is converted into useful mechanical power coming out the engine crankshaft. The rest of the energy (e.g., about 50%) is typically lost through the exhaust system (although partial recovery may occur through incorporating turbochargers or similar mechanisms driven by the exhaust). As fuel prices increase, method and systems for recovering some of this lost energy are increasingly desirable.
Previous attempts to incorporate a venturi within an exhaust system for a moving vehicle have failed to produce significant efficiency gains. Further, these prior art designs fail to be throttleable under a variety of combustion engine output states.